(Reuters) - Sony Corp (6758.T) is in the final stages of talks to invest 50 billion yen ($646 million) in cash-strapped Olympus Corp (7733.T), with an agreement expected by the end of September, state broadcaster NHK reported.

Sources familiar with the matter have told Reuters that Olympus is in talks with Sony to accept a cash injection in return for a stake. Medical device maker Terumo Corp (4543.T) and camera maker Fujifilm Holdings Corp (4901.T) have also said they are seeking to buy a stake in Olympus.

Endoscope maker Olympus needs a capital deal to mend its finances after it booked a net loss of 49 billion yen for the year ended on March 31, in the wake of a scandal over falsified financial statements and hidden investment losses.

In June, shareholders' equity had fallen to 2.2 percent of total assets from 4.6 percent in March. The ratio is a key barometer of a company's liquidity, with a 20 percent level widely regarded as indicative of financial stability.